Applied Mechanics and Materials Vols. 138-139

Abstract: The effects of phosphorus and organic carbon on bacterial growth were investigated in the laboratory. The bacteria sampled from the drinking water network of Tianjin were inoculated into water samples with different content of phosphorus (0～15µg PO₄^3--P/L) and assimilable organic carbon (10～200µgAOC/L). The inoculated water samples were incubated at 20°C. Bacterial growth was monitored in every 2 days in the beginning of cultivation and in every 4 days or more in the later of the cultivation. Results showed that Phosphorus had obvious promotion on bacterial growth, which included shortening the lag phase evidently, increasing the growth rate and the maximum cell count in stationary phase. Carbon can only increase bacterial number. Under oligotrophic condition，when ratio of AOC: P in nutrients of water was more than 100:5, phosphorus was the limiting factor of bacterial growth. The bacterial yield factors against phosphorus and AOC were 1.1×10⁹CFU/µgP and 9.0×10⁷CFU/µgAOC respectively. Phosphorus was more sensitive than AOC. When the phosphorus concentration was less than 0.7µg/L in water samples, it was very difficult for bacteria to obtain phosphorus, and then growth of bacteria was very slowly or in lag phase in the first nine days of incubation time. In drinking water with low concentration of phosphorus (<0.7µg/L) and disinfectants, bacterial regrowth may be controlled. The paper will be Narrated in two parts, “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (1)” and “Effects of AOC and Phosphorus on Bacterial Growth under Oligotrophic Condition (2)”.

Abstract: In this article, the partitioning behavior of C-phycocyanin (C-PC) in aqueous two-phase systems (ATPS) with different component was investigated to evaluate the applicability of ATPS for extracting high purity of C-PC without chromatography. Under the optimized conditions (pH = 6; PEG-2000, 16 %, w/w; potassium sodium tartrate 21 %, w/w), a maximum purity of 5.01 was achieved after the whole separation process and the yield of the C-PC was 76.94 %.

Abstract: The 10 organophosphorus pesticides in fish can be rapidly extracted and separated by gel permeation chromatography, and the lipin and organophosphorus pesticides of fish can be seperated. The interfering matters can be well eliminated in this condition, and analysis is more rapid than other methods. The residues of 10 organophosphorus pesticides at same time can be identified and quantified simultaneously by GC-PFPD. This method is simple, rapid, and the average recovery ratios were 71.7%-80.9%.Good repeatability was obtained in all the cases with relative standard deviations (RSDs) lower 11%, and limit of detection was0.0003-0.004 mg·kg^-1.

Abstract: The synthesis of a novel chitosan (CTS) derivative bearing β-cyclodextrin (β-CD) was studied, which was divided into two steps. The first step was the preparation of carboxymethyl-β-CD, then it was acyl chlorided. The second step was that β-CD was grafted onto the CTS skeleton by the reaction of acidamide. Its adsorption property on Pb²⁺ was investigated. The factors that influence on the effect were discussed, including adsorption time, pH value, and temperature. The results show that its adsorption content is superior to that of the unmodified CTS. And the adsorption content (Q_max) is 246 mg.g^-1 when the temperature is 35°C, pH is between 3.0~4.0 and adsorption time is 6 h.

Abstract: In order to improve the experimental evidence of hotoinitiator, the effects of various dose of photoinitiator on mechanical properties of nanohydroxyapatite composite were investigated. According to the light initiating system, CQ and DMAEMA accounted for 0.8wt％, 1.0wt％, 1.2wt％ of total resin matrix, respectively. And then NHA processed by KH-570 was mixed with resin matrix in the ratio of 55:45. Then three groups （A, B, and C） of light-cured nanohydroxyapatite composites were prepared. Karuisima composite resin was used as control group D. The cured depth, compressive strength, and flexural strength were determined in each group. The results showed that as the ratio of photoinitiator increased, the cured depth increased, while the mechanical function declined. In group B, there were no significant differences in compressive strength, and flexural strength as compared with control group, P>0.05. It is suggested that the quantity of CQ and DMAEMA in resin matrix were 1.0wt% respectively, the new light-cured nanohydroxyapatite composite has good qualities in both cured depth and mechanical property.

Abstract: Extrusion is an effective technology to increasing the contents of soluble dietary fibers (SDF). Response surface methodology (RSM) was applied to optimize operational parameters of extrusion. The determination coefficient (R²) was 0.80, and the results show that the regression models could explain the data variation and represent the actual relationships between the parameters and responses. The optimal operational parameters were: ratio of water 28%, zone temperature119.7 °C and rotation rate of screw 159.0 r/min. Under the optimal conditions, the maximum yield of SDF of 0.078 g/g in theory and 0.076 g/g in the experiment were obtained, with an increase of 15.1 % compared to the original yield (0.066 g/g) without extrusion process.

Abstract: .Various breads, pastries, fried bread stick, shrimp cracker, buns and other food samples were collected to detect the content of aluminum according to the method of CAS S-spectrophotometry from national standard GB 5009.182-2003, and health evaluation of flour products was carried out in accordance with GB2762-2005 "Standards of limit pollutants in food " (Al ≤ 100 mg/kg). 285 samples were qualified from 330 flour products, and the total qualified rate was 86.36%, and the content of aluminum content ranged from﹤0.5mg/kg to 255.1mg/kg. The content of aluminum of some samples like home-made steamed bread, stuffed buns, fried bread stick from canteens, small shops and supermarkets was higher than 100 mg/kg, in the range of 3.6-255.1, 28.0-217.2,7.6-185.8 mg/kg, and the qualified rate was 46.2%、61.1% and 35.3% respectively; The quality of other packaged food such as crackers, potato chips and so on was good.

Abstract: . The adsorption capacity of Orange II by Cetyltrimethyl Ammonium Bromide (CTAB)+bentonite mixture system and bentonite were tested and compared. The influence factors on removal rate of Orange II such as surfactant, the pH, the contact time and temperature were studied. The results showed that the presence of cationic surfactant such as CTAB could greatly enhance the removal efficiency compared with the system only bentonite supplied. The results showed that the highest removal rate of Orange II appeared on pH＜3, and when the pH value was from 3 to 5, the removal rate would drop 30%-50%.The effect of reaction temperature on the Orange II removal was then discussed, showed that the removal rate of Orange II descended 5%-10% when the temperature was higher than 25°C.

Abstract: A constant-volume visual cell was used to measure vapor-liquid phase equilibrium data of 2-butanol in supercritical carbon dioxide from 323.2K to 353.2K. The phase equilibrium solubilities were predicted by Peng-Robinson equation of state together with Vander Waals-2 mixing regulation. Dependence of solubility of CO₂ in liquid 2-butanol on pressure was discussed by Krichevsky-kasarnovsky equation. Meanwhile, Henry’s constants and partial molar volume at infinite dilution were determined. Also partial molar volumes of vapor phase and liquid phase at equation state were evaluated from proposed model. The correlation between calculated values and the experimental data showed good agreement.

Abstract: Purpose 1,1-DCE is a environmental pollutant of mutagenicity, carcinogenicity and teratogenicity. This paper studied the biodegradation of 1,1-DCE by two strains of aerobic bacteria which use benzene as co-metabolic substrate. Procedures First the two strains were activated, then through batch experiments, the residual concentrations of 1,1-DCE were monitored. Methods The biodegradation rates were determined, and the varying trends of the biodegradation rates with the initial concentrations were fitted by some kinetic models. Results The biodegradation kinetics of 1,1-DCE by the strain DB–I fits Monod Model, the corresponding parameters are ν_max=0.015h^-1, K_s＝10.18 mg·L^-1, while the biodegradation kinetics by strain DB-M fits Haldane Model, and the parameters respectively are ν_max =0.0063h^-1, K_s =4.55mg·L^-1，K_i=13.09mg·L^-1. Conclusion The specific substrate removal rate constant of 1,1-DCE by strain DB–I is higher than that of strain DB–M, and they are both higher than those of the studies performed by other authors.